VBScript

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VBScript

• Session 2

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What we learn last session?

• Data types.
• Declaring, assigning and usage of variables.
• Option Explicit statement.
• VBScript keywords (Null,True )
• Scope and liftime of variables.
• Rem statement.

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Subjets for Session 2

• Scalar variables and array variables.
• Redim statement.
• Preserve statement.
• Erase statement.
• Array function.
• LBound and UBound functions.

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Scalar Variables and Array Variables

• Much of the time, you only want to assign a
  single value to a variable you have declared.
• A variable containing a single value is a scalar
  variable.
• Other times, it is convenient to assign more than
  one related value to a single variable.
• Then you can create a variable that can contain a
  series of values.This is called an array
  variable.
• Array variables and scalar variables are declared
  in the same way, except that the declaration of
  an array variable uses parentheses ( ) following
  the variable name.

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Scalar Variables and Array Variables

• In the following example, a single-dimension
  array containing 11 elements is declared
• Dim A(10)
• Although the number shown in the parentheses is
  10, all arrays in VBScript are zero-based, so
  this array actually contains 11 elements.
• In a zero-based array, the number of array
  elements is always the number shown in
  parentheses plus one.
• This kind of array is called a fixed-size array.

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Scalar Variables and Array Variables

• You assign data to each of the elements of the
  array using an index into the array. Beginning at
  zero and ending at 10, data can be assigned to
  the elements of an array as follows

A(0) 256 A(1) 324 A(2) 100 . . . A(10)
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• Similarly, the data can be retrieved from any
  element using an index into the particular array
  element you want. For example

SomeVariable A(8)
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Scalar Variables and Array Variables

• Arrays aren't limited to a single dimension.
• You can have as many as 60 dimensions, although
  most people can't comprehend more than three or
  four dimensions.
• You can declare multiple dimensions by separating
  an array's size numbers in the parentheses with
  commas.
• In the following example, the MyTeble variable is
  a two-dimensional array consisting of 6 rows and
  11 columns

Dim MyTable(5, 10)
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Scalar Variables and Array Variables

• In a two-dimensional array, the first number is
  always the number of rows the second number is
  the number of columns.
• You can also declare an array whose size changes
  during the time your script is running.
• This is called a dynamic array. The array is
  initially declared within a procedure using
  either the Dim statement or using the Redim
  statement.

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ArraysRedim Statement

• ReDim Preserve varname(subscripts) ,
  varname(subscripts) . . .
• for a dynamic array, no size or number of
  dimensions is placed inside the parentheses. For
  example Dim MyArray()
• To use a dynamic array, you must subsequently use
  ReDim to determine the number of dimensions and
  the size of each dimension.
• A subsequent ReDim statement resizes the array to
  30, but uses the Preserve keyword to preserve the
  contents of the array as the resizing takes
  place.
• There is no limit to the number of times you can
  resize a dynamic array, although if you make an
  array smaller, you lose the data in the
  eliminated elements.

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ArraysRedim Statement

• for a dynamic array, no size or number of
  dimensions is placed inside the parentheses. For
  example

Dim MyArray()

• To use a dynamic array, you must subsequently use
  ReDim to determine the number of dimensions and
  the size of each dimension.
• A subsequent ReDim statement resizes the array to
  30, but uses the Preserve keyword to preserve the
  contents of the array as the resizing takes
  place.
• There is no limit to the number of times you can
  resize a dynamic array, although if you make an
  array smaller, you lose the data in the
  eliminated elements.

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Preserve Statement

• Preserves the data in an existing array when you
  change the size of the last dimension.
• If you use the Preserve keyword, you can resize
  only the last array dimension, and you can't
  change the number of dimensions at all.
• For example, if your array has only one
  dimension, you can resize that dimension because
  it is the last and only dimension.
• However, if your array has two or more
  dimensions, you can change the size of only the
  last dimension and still preserve the contents of
  the array

ReDim X(10, 10, 10) . . . ReDim Preserve X(10,
10, 15)
Caution    If you make an array smaller than it
was originally, data in the eliminated elements
is lost.
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Memory




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Erase Statement

• Reinitializes the elements of fixed-size arrays
  and deallocates dynamic-array storage space.
• Erase array
• It is important to know whether an array is
  fixed-size (ordinary) or dynamic because Erase
  behaves differently depending on the type of
  array.
• Erase recovers no memory for fixed-size arrays.
  Erase sets the elements of a fixed array as
  follows
• Fixed numeric array - Sets each element to zero.
• Fixed string array - Sets each element to
  zero-length ("").
• Array of objects - Sets each element to the
  special value Nothing.

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Erase Statement

• Erase frees the memory used by dynamic arrays.
• Before your program can refer to the dynamic
  array again, it must redeclare the array
  variable's dimensions using a ReDim statement.

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Array Function

• Returns a Variant containing an array.
• The required arglist argument is a
  comma-delimited list of values that are assigned
  to the elements of an array contained with the
  Variant.
• If no arguments are specified, an array of zero
  length is created.

Dim A A Array(10,20,30)
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LBound Function

• LBound(arrayname, dimension)
• Returns the smallest available subscript for the
  indicated dimension of an array.
• The dimension argument means a whole number
  indicating which dimension's lower bound is
  returned. Use 1 for the first dimension, 2 for
  the second, and so on. If dimension is omitted, 1
  is assumed
• The lower bound for any dimension is always 0.

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UBound Function

• UBound(arrayname, dimension)
• Returns the largest available subscript for the
  indicated dimension of an array.
• The dimension argument means a whole number
  indicating which dimension's lower bound is
  returned. Use 1 for the first dimension, 2 for
  the second, and so on. If dimension is omitted, 1
  is assumed
• The lower bound for any dimension is always 0.

Dim A(100,3,4) UBound (A, 1) 100 UBound (A, 2)
3 UBound (A, 3) 4
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Lab 2.1
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Lab 2.1

• Write a small program
• Declare using Dim 2 array variables.
• arr1 size of 5
• arr2 no size
• Assign descending values to arr1 (i.e.
  5,4,3,2..0)
• Resize the first array to 10, no data loss
• Resize the second array to 5.
• Print the content of the arrays to the reporter.

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